Multiple legal experts characterized President Yoon Suk Yeol's declaration of martial law as "clearly illegal" and "without justification" on social media posts and in conversation with The Korea Herald. The experts spoke on condition of anonymity due to the delicate nature of the situation.

Legal scholars drew parallels to former President Chun Doo-hwan's nationwide martial law declaration on May 17, 1980, which led to the Gwangju Democratic Uprising and the military's subsequent violent suppression of protesters.

The 1997 trials of Chun and top officials established a precedent that using martial law to suppress civil rights constitutes "subverting the Constitution" under Article 91 of the Criminal Act.

Article 91 defines constitutional subversion as acts that "extinguish the function of the Constitution or Acts without observing constitutional procedure" or "overthrow government bodies established by the Constitution or render the exercise of their functions impossible by force."

Under Article 87, those who engage in violence or riots with the explicit purpose of subverting the Constitution can be charged with insurrection, a crime that carries penalties of up to execution or life imprisonment for those in leadership roles. Those who aid or abet such actions face prison terms exceeding five years.

At least two experts said that law enforcement and military personnel who follow orders under the martial law declaration could be prosecuted under the same statutes. They said that participating in violent acts to support the declaration would qualify as aiding and abetting insurrection.

Opposition lawmaker Cho Kuk, leader of the liberal minor opposition Rebuilding Korea Party and former constitutional scholar, echoed these assessments after the parliament vote demanding the revoking of martial law.

"The act of declaring martial law itself is illegal, has no justifiable grounds or prerequisites," he said, singling out President Yoon Suk Yeol and Defense Minister Kim Yong-hyun as criminally punishable for the offense and calling for their impeachment.

Parliament voted unanimously to demand the nullification of martial law at 1:01 a.m. Wednesday, with all 190 members present voting in favor. Martial forces withdrew from the National Assembly building shortly after, the Speaker's office confirmed.